1. Field of the invention
This invention relates to a hydrogen storing member capable of storing hydrogen and a process for storing hydrogen into the hydrogen storing member, and particularly to a hydrogen storing member capable of storing hydrogen at a high concentration without scaling-up of an apparatus for storing hydrogen and a process for storing hydrogen into the hydrogen storing member. Thus, the present invention relates to a hydrogen storing member widely applicable to an apparatus for hydrogen purification and recovery, a heat pump, an apparatus for storing hydrogen, an actuator, an apparatus for cold nuclear fusion, etc. and a process for storing hydrogen into the hydrogen storing member.
2. Related Background Art
Recently, hydrogen has attracting attentions as a energy source in place of the fossil fuel. The attractive points of hydrogen are particularly that water is a raw material and thus hydrogen as a resource has no limit; hydrogen causes no environmental pollutions are brought about; hydrogen has a wide field of applications; hydrogen can serve as a means for storing other energy; and hydrogen can be used for energy transportation. Now, the transportation and storage of hydrogen are carried out in the form of a compressed hydrogen gas or liquefied hydrogen, which is not always regarded as an efficient process for transporting or storing hydrogen from the viewpoints of safety, transportation-storage efficiency and economy.
Recently, hydrogen storing materials are attracting attentions as a process for storing hydrogen, because hydrogen can be stored at a density equal to or higher than that of liquefied hydrogen.
As the process for storing hydrogen into a hydrogen storing member composed of a hydrogen storing alloy (metal), the following two main processes have been so far available. The first process is to bring about a vessel containing a hydrogen storing member into a hydrogen (light hydrogen) gas atmosphere compressed to a few to a few tens of atmospheres and utilize a solid solution equilibrium of a metal hydride composed of two elements, i.e. a metal and hydrogen under a high pressure, thereby conducting hydrogen storage. The second process is to use a hydrogen storing alloy as a cathode and storing hydrogen (light hydrogen) generated at the cathode by electric current passage into the hydrogen storing alloy as an application of water electrolysis.
Usually, the hydrogen content in the hydrogen storing material according to the first process depends upon the hydrogen gas pressure in the vessel and the temperature of the hydrogen storing alloy, and the hydrogen content abruptly increases with higher pressure of the hydrogen gas or lower temperature of the hydrogen storing material. When a metal or an alloy is used as a hydrogen storing material in this manner, hydrogen storage is carried out by utilizing the phenomenon that the structure of the hydrogen storing material depends upon the temperature or the pressure and thus the quantity of stored hydrogen is also changed thereby.
In the second electrolysis process, the pressure on the cathode surface depends upon the applied voltage at the electrolysis and thus the pressure on the cathode surface can be increased from a few atmospheres to a few tens of atmospheres by increasing the voltage.
On the other hand, very recently, nuclear fusion using a hydrogen storing member has been reported and the usefulness of the hydrogen storing member in the nuclear fusion has been pointed. That is, in the so far proposed nuclear fusion processes, a high temperature plasma of deuterium is maintained by the action of magnetic field, or compressed to a high density, and the nuclear fusion reaction is carried out before the scattering of the plasma. Thus, in order to maintain the high temperature plasma in a confined state for a long time, a very large apparatus based on the Tokamak system has been used. On the other hand, it has been recently reported that cold nuclear fusion can be generated according to a simple process for electrolysing a heavy water solution containing many kinds of metal ions, using a hydrogen storing member composed of a simple metal such as Pd, Ti, etc. as a cathode. The cold nuclear fusion is carried out by combining deuteriums themselves in a hydride of Pd or Ti by electrolysis, using a simple metal of Pd or Ti capable of deuterium as a cathode. For example, S. E. Jones et. al. reported in Nature 338 (1989) 737 "observation of cold nuclear fusion in condensed matter" that neutrons generated during the electrolysis were measured by a high sensitive detector and neutrons of 2.5 MeV were detected thereby, and proved that the nuclear fusion reaction took place to a very slight degree. Thus, the hydrogen storing member and a process for storing hydrogen are attracting attentions in the nuclear fusion.
However, the process requiring a high pressure or a low temperature in storing hydrogen into the hydrogen storing member has such problems as scale-up of the apparatus for carrying out the process, an increase in the operating cost and a difficulty to control the atmosphere in which the hydrogen storing member is placed (control of pressure, etc.)
On the other hand, particularly in case of applying the hydrogen storing member to the nuclear fusion, thereby occasioning the nuclear fusion reaction efficiently, deuterium must be stored in excess in the hydrogen storing member. In the conventional process it was impossible to store the deuterium in much excess in the hydrogen storing member. For this reason, the probability of nuclear fusion reaction was low and the absolute amount of detected neutrons was very small.